normally within 24hrs, telco will say 3-5 business days though.
will need to clear all outstanding bill from current telco and there will be a last bill after port out, that's the beauty of postpaid🙊

For prepaid yes, normally within 48 hours all complete.

For postpaid, might delay a bit because billing need to be checked..
However, no need to worry. As long your previous bill paid on time. There will be last bill, maybe on 18th Sept, if by 18th Aug process not completed.

Usually will complete in 24 to 48 hours. However, do watch out for any messages from time to time. My experience with porting out Digi postpaid to Hotlink postpaid, Digi sent me an amount to pay after a few hours of replying to the port out confirmation.
Have I not notice the SMS and pay the bill, my port out would fail.